"},{"ID":418698,"user_firstname":"Isabella","user_lastname":"Toschi","nickname":"Isabella Toschi","user_nicename":"itoschi","display_name":"Isabella Toschi","user_email":"itoschi@esri.com","user_url":"","user_registered":"2025-11-04 13:34:22","user_description":"Isabella Toschi is a Senior Product Engineer at Esri and the Product Owner for the Alignment in Reality Studio. She has extensive experience in 3D vision systems, with a particular focus on aerial triangulation of airborne imagery. She is passionate about measurement and applies this drive to enhance image alignment capabilities and ensure accurate and precise Reality Mapping products.","user_avatar":"
"}],"short_description":"This article explains why control points are key to survey-grade accuracy and how you can measure them efficiently in ArcGIS Reality Studio.","flexible_content":[{"acf_fc_layout":"content","content":"The Image Measurement Tool in ArcGIS Reality Studio
\nData courtesy for all images in this article: City of Stuttgart and GeoFly GmbH<\/a><\/p><\/blockquote>\nThis article explains why control points are key to survey-grade accuracy and how the Image Measurement Tool in ArcGIS Reality Studio helps you measure\u00a0<\/span>and manage\u00a0<\/span>them more efficiently.<\/span>\u00a0<\/span><\/p>\n
Why do I need control points for survey-grade\u00a0accuracy?\u00a0<\/strong><\/h2>\n
Photogrammetry allows large areas to be mapped efficiently. After capture, however, one of the most time-consuming steps is measuring ground control points (GCPs)<\/span>\u00a0and check points (CPs)<\/span>. Despite the effort, this step is\u00a0<\/span>important<\/span>\u00a0<\/span>for ensuring\u00a0accurate\u00a0results and\u00a0facilitating\u00a0a thorough quality assessment.<\/span>\u00a0<\/span><\/p>\n
During bundle block adjustment, overlapping images are aligned\u00a0relative\u00a0to each other. This results in strong internal consistency, meaning the geometry within the dataset is precise. However, the\u00a0<\/span>absolute accuracy<\/span><\/b>\u00a0of the\u00a0<\/span>subsequent\u00a0<\/span>reconstruction depends on the quality of the<\/span>\u00a0<\/span>input trajectory,\u00a0<\/span>that is<\/span>,<\/span>\u00a0the<\/span>\u00a0camera position<\/span>s and rotations<\/span>\u00a0during image capture.\u00a0<\/span>If this information is not sufficiently\u00a0accurate<\/span>, the entire block may be shifted or misaligned in real-world coordinates.<\/span>\u00a0<\/span>Ground c<\/span>ontrol points anchor the block to\u00a0<\/span>accurate\u00a0<\/span>known coordinates and ensure correct absolute positioning.<\/span>\u00a0<\/span><\/p>\n
Control points<\/span>\u00a0also enable\u00a0<\/span>quality assessment<\/span><\/b>. By defining some points as\u00a0<\/span>check points<\/span>,<\/span><\/b>\u00a0you can\u00a0<\/span>independently\u00a0<\/span>evaluate\u00a0<\/span>the\u00a0<\/span>accuracy\u00a0<\/span>of your aligned results<\/span>.\u00a0<\/span>As\u00a0<\/span>their 3D coordinates are not used during the adjustment, t<\/span>heir\u00a0<\/span>3D\u00a0<\/span>residuals<\/span>\u00a0(<\/span>the difference between known and\u00a0<\/span>estimated<\/span>\u00a0positions<\/span>)\u00a0<\/span>provide a clear\u00a0<\/span>and\u00a0<\/span>unbiased<\/span>\u00a0<\/span>indication\u00a0of how well the model fits reality.<\/span>\u00a0<\/span><\/p>\n
In multi-flight projects,\u00a0<\/span>ground\u00a0<\/span>control points also\u00a0<\/span>connect separate image blocks<\/span><\/b>\u00a0into one consistent result.<\/span>\u00a0Shared control points allow these blocks to be connected and aligned, creating a consistent overall result and helping compensate for systematic effects.<\/span>\u00a0<\/span><\/p>\n
\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"content","content":"
How can I measure control points efficiently?\u00a0<\/strong><\/h2>\n
Each control point must be measured in multiple images to link its real-world coordinates with pixel positions. While two measurements are sufficient to triangulate a point,\u00a0additional\u00a0observations improve robustness<\/span>\u00a0–\u00a0<\/span>especially when captured from different viewing angles.<\/span>\u00a0<\/span><\/p>\n
In practice, measuring the same point across many images can quickly become the most time-consuming part of the workflow.<\/span>\u00a0<\/span><\/p>\n
To support this, the Image Measurement Tool\u00a0<\/span>in ArcGIS Reality Studio\u00a0<\/span>provides\u00a0<\/span>point suggestions<\/span><\/b>. After measuring a point in\u00a0<\/span>two or more<\/span>\u00a0images, the tool suggests its location in\u00a0additional\u00a0images. This reduces the need for manual search and speeds up the process significantly.<\/span>\u00a0<\/span><\/p>\n
Performing\u00a0an initial\u00a0alignment in advance enhances both the quantity and reliability of point suggestions, as the optimized camera positions provide a stronger foundation for\u00a0accurate\u00a0predictions.<\/span>\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2970645,"id":2970645,"title":"IMT-Suggestions","filename":"IMT-Suggestions-2-scaled.png","filesize":833270,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-scaled.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgisrealitystudio\/imagery\/measuring-and-managing-control-points-efficiently-in-arcgis-reality-studio\/imt-suggestions-2","alt":"Point suggestions (red marker) in the Image Measurement Tool in ArcGIS Reality Studio","author":"422580","description":"","caption":"Point suggestions (red marker) in the Image Measurement Tool \nin ArcGIS Reality Studio ","name":"imt-suggestions-2","status":"inherit","uploaded_to":2970603,"date":"2026-06-16 13:24:29","modified":"2026-06-16 13:30:42","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":2560,"height":1899,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-scaled.png","medium-width":352,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-scaled.png","medium_large-width":768,"medium_large-height":570,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-scaled.png","large-width":1456,"large-height":1080,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-1536x1140.png","1536x1536-width":1536,"1536x1536-height":1140,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-2048x1519.png","2048x2048-width":2048,"2048x2048-height":1519,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-627x465.png","card_image-width":627,"card_image-height":465,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-1456x1080.png","wide_image-width":1456,"wide_image-height":1080}},"image_position":"center","orientation":"horizontal","hyperlink":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Suggestions-2-scaled.png"},{"acf_fc_layout":"content","content":"
How does the map support point management?\u00a0<\/strong><\/h2>\n
Accurate georeferencing depends not only on precise point measurements but also on a well-planned spatial distribution of\u00a0ground control\u00a0and check points. Being able to evaluate this distribution early in the workflow is key.<\/span>\u00a0<\/span><\/p>\n
The Image Measurement Tool introduces a map-centric approach that helps you do exactly that.<\/span>\u00a0<\/span><\/p>\n
From the map view, you can select, filter, and create points directly within the project area. Once a point is selected, you can\u00a0immediately\u00a0measure it in the images. This\u00a0<\/span>connection between map and image space<\/span><\/b>\u00a0helps you quickly decide where\u00a0additional\u00a0measurements are needed.\u00a0The\u00a0map centric user interface\u00a0helps\u00a0to achieve a\u00a0good spatial coverage across the entire project while keeping the measurement process efficient.<\/span>\u00a0<\/span><\/p>\n
Filtering options support a\u00a0<\/span>quick assessment<\/span><\/b>\u00a0of how\u00a0ground\u00a0control points and check points are distributed. A well-balanced set of\u00a0ground\u00a0control points contributes to stable georeferencing, while evenly distributed check points allow for meaningful accuracy evaluation across the full extent of the dataset.<\/span>\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2970648,"id":2970648,"title":"IMT-Map","filename":"IMT-Map-2-scaled.png","filesize":1167103,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-scaled.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgisrealitystudio\/imagery\/measuring-and-managing-control-points-efficiently-in-arcgis-reality-studio\/imt-map-3","alt":"","author":"422580","description":"The Map of the Image Measurement Tool offers functionalities to filter, select, create and define the role of points on a common base map","caption":"The Map of the Image Measurement Tool offers functionalities to filter, select, create and define the role of points on a common base map","name":"imt-map-3","status":"inherit","uploaded_to":2970603,"date":"2026-06-16 13:27:34","modified":"2026-06-16 13:31:43","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":2560,"height":1739,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-scaled.png","medium-width":384,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-scaled.png","medium_large-width":768,"medium_large-height":522,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-scaled.png","large-width":1590,"large-height":1080,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-1536x1044.png","1536x1536-width":1536,"1536x1536-height":1044,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-2048x1391.png","2048x2048-width":2048,"2048x2048-height":1391,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-684x465.png","card_image-width":684,"card_image-height":465,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-1590x1080.png","wide_image-width":1590,"wide_image-height":1080}},"image_position":"center","orientation":"horizontal","hyperlink":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-2-scaled.png"},{"acf_fc_layout":"content","content":"
By visualizing the automatic tie points generated during the Alignment, the map also helps\u00a0<\/span><\/span>identify<\/span>\u00a0areas with weak\u00a0<\/span>connection<\/span><\/span><\/strong>. In such regions, you can create\u00a0<\/span><\/span>manual tie points<\/span><\/span>\u00a0– points without known field coordinates – that strengthen the block by adding image observations where automatic tie points are sparse.<\/span><\/span>\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2970642,"id":2970642,"title":"IMT-Map-with-Tiepoints","filename":"IMT-Map-with-Tiepoints-1-scaled.png","filesize":4367895,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-scaled.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgisrealitystudio\/imagery\/measuring-and-managing-control-points-efficiently-in-arcgis-reality-studio\/imt-map-with-tiepoints-2","alt":"","author":"422580","description":"Visualization of Automatic Tie Points, along with ground control points and check points in the Image Measurement Tool Map","caption":"Visualization of Automatic Tie Points, along with ground control points and check points in the Image Measurement Tool Map","name":"imt-map-with-tiepoints-2","status":"inherit","uploaded_to":2970603,"date":"2026-06-16 13:22:29","modified":"2026-06-16 13:32:21","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":2560,"height":1739,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-scaled.png","medium-width":384,"medium-height":261,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-scaled.png","medium_large-width":768,"medium_large-height":522,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-scaled.png","large-width":1590,"large-height":1080,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-1536x1044.png","1536x1536-width":1536,"1536x1536-height":1044,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-2048x1391.png","2048x2048-width":2048,"2048x2048-height":1391,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-684x465.png","card_image-width":684,"card_image-height":465,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-1590x1080.png","wide_image-width":1590,"wide_image-height":1080}},"image_position":"center","orientation":"horizontal","hyperlink":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Map-with-Tiepoints-1-scaled.png"},{"acf_fc_layout":"content","content":"
How can I evaluate measurement quality?\u00a0<\/strong><\/h2>\n
Points\u2019\u00a0measurement quality\u00a0and distribution\u00a0directly\u00a0influence\u00a0the\u00a0accuracy\u00a0of the alignment and\u00a0of the derived\u00a0final outputs. Understanding and interpreting this quality is therefore\u00a0an important step\u00a0in the workflow.\u00a0<\/span>\u00a0<\/span><\/p>\n
The\u00a0<\/span>Image Measurement Tool provides<\/span>\u00a0these indicators to\u00a0identify\u00a0inconsistencies or gaps in the dataset and guide further refinement:<\/span>\u00a0<\/span><\/p>\n
\n
- Reprojection error\u00a0<\/span><\/b>describes\u00a0how well a 3D point fits its observed image positions.\u00a0It is calculated as the difference between the measured pixel location and the projected position of the reconstructed 3D point back into the image. Higher values\u00a0(e.g.<\/span>\u00a0<\/span>above\u00a02\u00a0pixels)\u00a0often\u00a0indicate\u00a0inconsistent or imprecise image measurements.<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\n
- 3D residuals<\/span><\/b>\u00a0represent\u00a0the difference between the known real-world coordinates of a point and its\u00a0estimated\u00a0position after adjustment. They provide a direct measure of positional accuracy in object space.<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\n
- Point distribution<\/span><\/b>\u00a0on the map\u00a0reflects how well\u00a0ground\u00a0control points and check points are spread across the project area. A balanced distribution is essential for a stable and reliable solution.<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\u00a0A\u00a0high reprojection error may suggest revisiting image measurements for that point, while large 3D residuals can\u00a0indicate\u00a0issues with point accuracy. An uneven spatial distribution\u00a0of points\u00a0may highlight areas where additional control points or\u00a0manual\u00a0tie points are needed to stabilize the solution.<\/span>\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2970609,"id":2970609,"title":"IMT-Table","filename":"IMT-Table.png","filesize":327085,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgisrealitystudio\/imagery\/measuring-and-managing-control-points-efficiently-in-arcgis-reality-studio\/imt-table","alt":"Control points table in the Image Measurement Tool to evaluate quality parameters for informed decision making of next fine-tuning steps","author":"422580","description":"Control points table in the Image Measurement Tool to evaluate quality parameters for informed decision making of next fine-tuning steps","caption":"Control points table in the Image Measurement Tool to evaluate quality parameters for informed decision making of next fine-tuning steps","name":"imt-table","status":"inherit","uploaded_to":2970603,"date":"2026-06-16 08:39:33","modified":"2026-06-16 08:39:40","menu_order":0,"mime_type":"image\/png","type":"image","subtype":"png","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":1908,"height":958,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table-213x200.png","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","medium-width":464,"medium-height":233,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","medium_large-width":768,"medium_large-height":386,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","large-width":1908,"large-height":958,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table-1536x771.png","1536x1536-width":1536,"1536x1536-height":771,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","2048x2048-width":1908,"2048x2048-height":958,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table-826x415.png","card_image-width":826,"card_image-height":415,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2026\/06\/IMT-Table.png","wide_image-width":1908,"wide_image-height":958}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":"
Key benefits of the Image Measurement Tool\u00a0<\/strong><\/h2>\n
Control points\u00a0remain\u00a0essential for achieving survey-grade accuracy, but they have traditionally required significant manual effort. The Image Measurement Tool in ArcGIS Reality Studio streamlines\u00a0the measurement\u00a0process and improves both efficiency and quality.<\/span>\u00a0<\/span><\/p>\n
Key benefits include:<\/span>\u00a0<\/span><\/p>\n
\n
- Faster measurements<\/span><\/b>\u00a0through intelligent point suggestions, reducing manual effort across images<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\n
- Map-based point management<\/span><\/b>\u00a0that allows you to create, filter, and evaluate control and check points directly in spatial context<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\n
- Better control over spatial distribution<\/span><\/b>\u00a0by visualizing point coverage and identifying gaps early\u00a0in the\u00a0workflow\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
\n
- Informed decision-making<\/span><\/b>\u00a0with clear quality indicators such as reprojection\u00a0errors and\u00a03D\u00a0residuals that guide refinement and ensure reliable and accurate results<\/span>\u00a0<\/span><\/li>\n<\/ul>\n
Together, these capabilities make measuring and managing control points more efficient, transparent, and scalable\u00a0–\u00a0helping you achieve accurate and consistent reality mapping results with less effort.<\/span>\u00a0<\/span><\/p>\n"},{"acf_fc_layout":"youtube","start_time":"0","end_time":"","youtube_video_url":"https:\/\/mediaspace.esri.com\/playlist\/dedicated\/1_0r65usuk\/1_dc0b2hz7<\/a>"},{"acf_fc_layout":"content","content":"
Get started with the Image Measurement Tool\u00a0<\/strong><\/h2>\n
For a step-by-step introduction to the workflow, explore this video series<\/a> <\/span>that goes through everything covered in this article!<\/span><\/p>\n
For a detailed written overview, you can check out the ArcGIS Reality Studio documentation<\/a><\/span> as well.<\/span><\/p>\n
<\/p>\n
To learn more about ArcGIS Reality, you can visit our product page<\/a> and check the resources<\/a>. Follow us on LinkedIn<\/a><\/span>\u00a0to receive recent development updates on Esri\u2019s Reality products.<\/span><\/p>\n